EM quantitative studies will be carried out to determine the presence and origin of H3 RNA in prebanglionic fibers and giant presynaptic terminals of the chick ciliary ganglion after intraventricular injection of H3 uridine at the level of the Edinger-Westphal nucleus. An attempt will be made to determine whether the axonal RNA that we have found by EM autoradiography of the rabbit optic nerve after intraocular injection of H3 uridine is provided by axonal flow or is a result of local synthesis. Autoradiography of the optic nerve will be carried out (a) after intraocular injection of H3 uridine and actinomycin A, (b), at different times after intracranial injection of H3 uridine. The nature of the radioactivity present in synaptosomal fractions after incubation with H3 leucine in the presence of cycloheximide will be investigated. It will be determined (a) whether the radioactivity is present as leucine and is not due to a minor impurity present in the precursor and (b), whether leucine is in a peptide bond. If so, (c), the gel electrophoretic pattern of the radioactive protein will be compared to that of control fractions. The nature of the in vitro incorporation of H3 leucine by fractions of myelinated axons will be investigated by N terminal analysis and gel electrophoresis. The labeled glycoproteins recovered in the myelin fractions of optic nerve after intraocular injection of H3 fucose will be further studied in order to determine their location.